LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 274 (Lighting System - DTC B3891 To DTC C0297 And Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC B3948 or B3949: Front Turn Signal Circuits >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.

DTC B3948

  1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E4 Turn Signal Lamp - Left Front. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 15 Ω between the appropriate ground circuit terminal listed below and ground.
    • E4Y Turn Signal Repeater Lamp - Left terminal 1
    • E4LF Turn Signal Lamp - Left Front terminal G (with T4F)
    • E4LF Turn Signal Lamp - Left Front terminal G (TR6-T4F)
    • E4N Park/Turn Signal Lamp - Left terminal G (TUJ-T4F)
    • If 15 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • If less than 15 Ω 
  3. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.
    • E4Y Turn Signal Repeater Lamp - Left terminal 2
    • E4LF Turn Signal Lamp - Left Front terminal A (with T4F)
    • E4LF Turn Signal Lamp - Left Front terminal A (TR6-T4F)
    • E4N Park/Turn Signal Lamp - Left terminal A (TUJ-T4F)
  4. Verify the test lamp turns ON and OFF when commanding the Left Front Turn Signal Lamp ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the control circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K9 Body Control Module.
    • If the test lamp turns ON and OFF 
  5. Test or replace the E4 Turn Signal Lamp - Left Front.

DTC B3949

  1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E4 Turn Signal Lamp - Right Front. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 15 Ω between the appropriate ground circuit terminal listed below and ground.
    • E4Z Turn Signal Repeater Lamp - Right terminal 1
    • E4RF Turn Signal Lamp - Right Front terminal G (with T4F)
    • E4RF Turn Signal Lamp - Right Front terminal G (TR6-T4F)
    • E4P Park/Turn Signal Lamp - Right terminal G (TUJ-T4F)
    • If 15 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • If less than 15 Ω 
  3. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.
    • E4Z Turn Signal Repeater Lamp - Right terminal 2
    • E4RF Turn Signal Lamp - Right Front terminal A (with T4F)
    • E4RF Turn Signal Lamp - Right Front terminal A (TR6-T4F)
    • E4P Park/Turn Signal Lamp - Right terminal A (TUJ-T4F)
  4. Verify the test lamp turns ON and OFF when commanding the Right Front Turn Signal Lamp ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the control circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K9 Body Control Module.
    • If the test lamp turns ON and OFF 
  5. Test or replace the E4 Turn Signal Lamp - Right Front.
scientia non olet · About LEMON Manuals